Hydraulic shovel work amount detection apparatus, work amount detection method, work amount detection result display apparatus

ABSTRACT

During transfer of a material by a hydraulic excavator, load computing means periodically computes the weight of the material in a bucket of the excavator. Average value computing means computes an average value of weights of the material including a currently computed weight and a predetermined number of weights computed prior to the currently computed weight (M 6 ), and standard deviation computing means computes, based on the average value, a standard deviation of the weights of the material (M 7 ). True load value determining means selects a minimum standard deviation from among the standard deviations computed by the standard deviation computing means from the start of the transfer of the material to a different location until the end of the transfer of same, and judges the average value based on which the minimum standard deviation was computed, to be a true value of the weight of the material (M 10 , M 11 ).

TECHNICAL FIELD

The present invention relates to a work amount detection device andmethod and work amount detection result display device for a hydraulicexcavator, and more particularly, to a device and method for detectingthe work amount of a hydraulic excavator used at a mine or the like forloading dump trucks with mineral ore etc., and a device for displayingthe results of detection of the work amount of such a hydraulicexcavator.

BACKGROUND ART

A hydraulic excavator used at a mine etc. operates in the followingmanner: When a dump truck is stopped near the hydraulic excavator, theexcavator scoops mineral ore or earth/sand from an excavation spot witha bucket thereof, swings by means of a revolving superstructure thereofto move the bucket to a position above the vessel of the dump truck, andthen releases and loads the scooped mineral ore or earth/sand onto thevessel. Then, to again load the dump truck with mineral ore orearth/sand, the hydraulic excavator swings toward the excavation spot bymeans of the revolving superstructure. The hydraulic excavator repeatsthe above sequence of operations several times to load the vessel of thedump truck with a predetermined amount of mineral ore or earth/sand.After the loading is completed, the dump truck transports the mineralore or earth/sand to a prespecified location.

While the loading is performed, a mine supervisor or the like needs tomeasure the amounts of loads placed on dump trucks by the hydraulicexcavator, in order to manage the output of the mineral ore orearth/sand. The task is easy if dump trucks are equipped with movableload meters, but many of dump trucks do not have such load meters. Also,it is difficult to estimate the amount of load from the capacity of thevessel, because the vessel capacity varies depending on the types ofdump trucks. Thus, with dump trucks alone, it is not easy to measureloads placed thereon.

Conventionally, when measuring the amount of mineral ore or earth/sandloaded onto a dump truck by a hydraulic excavator, the operator of theexcavator operates a measurement button immediately before the mineralore or earth/sand is loaded onto the dump truck, to measure the weightof the mineral ore or earth/sand.

There have also been proposed techniques for automatically measuring theweight of mineral ore or earth/sand scooped in the bucket. For example,Unexamined Japanese Patent Publication No. H06-10378 discloses atechnique whereby a load in the bucket detected before the bucket isoperated or swung is regarded as the load amount. Unexamined JapanesePatent Publication No. H07-259137 discloses a technique whereby a loadin the bucket detected when the swing speed of the arm is lower than afixed speed and at the same time the swing speed of the boom is higherthan a fixed speed is regarded as the load amount. Also, UnexaminedJapanese Patent Publication No. S62-274223 discloses a technique wherebycylinder oil pressures detected before and after the bucket reaches apredetermined height are averaged and a load in the bucket calculatedfrom the average oil pressure is regarded as the load amount.

However, the aforementioned conventional method and the techniquesdisclosed in the publications are associated with problems. Namely, evenin cases where the load in the bucket is unstable because ofaccelerating/decelerating operation of the boom or the arm or due toother factors, the load in the bucket is measured automatically or inresponse to operation of the measurement button, with the result thatthe amount of mineral ore or earth/sand loaded onto a dump truck cannotbe measured with accuracy.

Also, the techniques disclosed in Unexamined Japanese Patent PublicationNo. H07-259137 and Unexamined Japanese Patent Publication No. S62-274223are associated with a problem that the measurement itself cannot beachieved when predetermined conditions (predetermined swing speed,predetermined bucket height) are not fulfilled.

If the amount of mineral ore or earth/sand loaded onto dump truckscannot be measured with accuracy, then it is not possible to accuratelymanage the output of the mineral ore or earth/sand.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a work amount detectiondevice and method and a work amount detection result display device fora hydraulic excavator whereby the weight of mineral ore or earth/sandloaded onto a dump truck can always be measured with accuracy, thuspermitting accurate management of the output of the mineral ore orearth/sand.

To achieve the object, there is provided a work amount detection devicefor a hydraulic excavator which scoops a material with a bucket thereofand transfers the material to a different location, wherein the workamount detection device comprises: transfer start detecting means fordetecting start of the transfer of the material to the differentlocation; transfer end detecting means for detecting end of the transferof the material to the different location; load computing means forperiodically computing weight of the material in the bucket during thetransfer; average value computing means for computing an average valueof weights of the material periodically computed by the load computingmeans, the weights of the material including a currently computed weightand a predetermined number of weights computed prior to the currentlycomputed weight; standard deviation computing means for computing, basedon the average value computed by the average value computing means, astandard deviation of the weights of the material including thecurrently computed weight and the predetermined number of weightscomputed prior to the currently computed weight; and true load valuedetermining means for selecting a minimum standard deviation from amongthe standard deviations computed by the standard deviation computingmeans from the start of the transfer of the material to the differentlocation until the end of the transfer of same, and judging the averagevalue based on which the minimum standard deviation was computed, to bea true value of the weight of the material.

Thus, in the work amount detection device for a hydraulic excavator, theweight of the material in the bucket is periodically computed by theload computing means during the transfer of the material. In addition,the average value computing means computes an average value of weightsof the material including a currently computed weight and apredetermined number of weights computed prior to the currently computedweight, and based on the average value, the standard deviation computingmeans computes a standard deviation of the weights of the materialincluding the currently computed weight and the predetermined number ofweights computed prior to the currently computed weight. The true loadvalue determining means selects a minimum standard deviation, from amongthe standard deviations computed by the standard deviation computingmeans from the start of the transfer of the material to a differentlocation until the end of the transfer of the material, and judges theaverage value based on which the minimum standard deviation wascomputed, to be a true value of the weight of the material.

It is therefore possible to extract, as a true value of the weight ofthe material, the weight of the material computed during a period inwhich the standard deviation of detected weights is a minimum and thusthe weight of the material is stable while the material is transferredto a different location. Accordingly, the weight of the material canalways be measured with accuracy in an appropriate manner irrespectiveof movements (boom moving speed, arm moving speed, bucket height, etc.)of the hydraulic excavator, thus permitting accurate management of theoutput of mineral ore or earth/sand as the material.

There is also provided a work amount detection device for a hydraulicexcavator which scoops a material with a bucket thereof and transfersthe material to a transportation vehicle, wherein the work amountdetection device comprises: teaching means for teaching a position forthe transportation vehicle; transportation vehicle detecting means fordetecting the transportation vehicle when the transportation vehicle islocated at the position taught by the teaching means; transfer startdetecting means for detecting start of the transfer of the material tothe transportation vehicle; transfer end detecting means for detectingend of the transfer of the material to the transportation vehicle; loadcomputing means for periodically computing weight of the material in thebucket during the transfer; average value computing means for computingan average value of weights of the material periodically computed by theload computing means, the weights of the material including a currentlycomputed weight and a predetermined number of weights computed prior tothe currently computed weight; standard deviation computing means forcomputing, based on the average value computed by the average valuecomputing means, a standard deviation of the weights of the materialincluding the currently computed weight and the predetermined number ofweights computed prior to the currently computed weight; and true loadvalue determining means for selecting a minimum standard deviation fromamong the standard deviations computed by the standard deviationcomputing means from the start of the transfer of the material to thetransportation vehicle until the end of the transfer of same, andjudging the average value based on which the minimum standard deviationwas computed, to be a true value of the weight of the material.

Also with this work amount detection device for a hydraulic excavator,it is possible to extract, as a true value of the weight of thematerial, the weight of the material computed during a period in whichthe standard deviation of detected weights is a minimum and thus theweight of the material is stable while the material is transferred tothe transportation vehicle, and accordingly, the weight of the materialcan always be measured with accuracy in an appropriate mannerirrespective of movements (boom moving speed, arm moving speed, bucketheight, etc.) of the hydraulic excavator. Moreover, the teaching meansteaches a position for the transportation vehicle, and thetransportation vehicle detecting means detects the transportationvehicle when the vehicle is located at the taught position, thuspermitting reliable loading of the material onto the transportationvehicle. In cases where the material is transported using transportationvehicles, therefore, the actual output of mineral ore or earth/sand asthe material can be managed with accuracy.

In the work amount detection device, the transfer start detecting meansmay detect, as the start of the transfer, completion of scooping of thematerial with the bucket, and the transfer end detecting means maydetect, as the end of the transfer, bucket dump operation.

Thus, it is possible to obtain standard deviations of detected weightsof the material over the longest possible transfer period, that is, fromthe completion of scooping of the material with the bucket (end ofexcavation) to the dumping (release) of the material out of the bucket,whereby a true value of the weight of the material can be determinedbased on weights detected over a wide range.

There is also provided a work amount detection method for a hydraulicexcavator which scoops a material with a bucket thereof and transfersthe material to a different location, wherein the work amount detectionmethod comprises: a transfer start detecting step of detecting start ofthe transfer of the material to the different location; a transfer enddetecting step of detecting end of the transfer of the material to thedifferent location; a load computing step of periodically computingweight of the material in the bucket during the transfer; an averagevalue computing step of computing an average value of weights of thematerial periodically computed in the load computing step, the weightsof the material including a currently computed weight and apredetermined number of weights computed prior to the currently computedweight; a standard deviation computing step of computing, based on theaverage value computed in the average value computing step, a standarddeviation of the weights of the material including the currentlycomputed weight and the predetermined number of weights computed priorto the currently computed weight; and a true load value determining stepof selecting a minimum standard deviation from among the standarddeviations computed in the standard deviation computing step from thestart of the transfer of the material to the different location untilthe end of the transfer of same, and judging the average value based onwhich the minimum standard deviation was computed, to be a true value ofthe weight of the material.

Thus, according to the work amount detection method for a hydraulicexcavator, the weight of the material in the bucket is periodicallycomputed in the load computing step during the transfer of the material.In addition, an average value of weights of the material including acurrently computed weight and a predetermined number of weights computedprior to the currently computed weight is calculated in the averagevalue computing step, and based on the average value, a standarddeviation of the weights of the material including the currentlycomputed weight and the predetermined number of weights computed priorto the currently computed weight is computed in the standard deviationcomputing step. Then, in the true load value determining step, a minimumstandard deviation is selected from among the standard deviationscomputed in the standard deviation computing step from the start of thetransfer of the material to a different location until the end of thetransfer of the material, and the average value based on which theminimum standard deviation was computed is judged to be a true value ofthe weight of the material.

Accordingly, the weight of the material can always be measured withaccuracy in an appropriate manner, making it possible to manage withaccuracy the output of mineral ore or earth/sand as the material, likethe above work amount detection device.

In the work amount detection method, completion of scooping of thematerial with the bucket may be detected in the transfer start detectingstep as the start of the transfer, and bucket dump operation may bedetected in the transfer end detecting step as the end of the transfer.

This permits a true value of the weight of the material to be determinedbased on weights detected over a wide range, as in the above work amountdetection device.

There is also provided a work amount detection result display device fora hydraulic excavator which comprises, in addition to the individualelements of the work amount detection device, weight display means fordisplaying at least an integrated value of the true values determined bythe true load value determining means over a predetermined period.

This makes it easy for the operator of the hydraulic excavator toconfirm an accurate weight of the material transferred over thepredetermined period.

In the work amount detection result display device, the weight displaymeans may display an integrated value of the true values determined bythe true load value determining means over a period from the time anengine ignition key of the hydraulic excavator is turned ON until theengine ignition key is turned OFF.

This makes it easy for the operator of the hydraulic excavator or asupervisor to confirm an accurate weight of the material transferredduring each work shift period.

There is also provided a work amount detection result display device fora hydraulic excavator which scoops a material with a bucket thereof andtransfers the material to a transportation vehicle, wherein the workamount detection result display device comprises: teaching means forteaching a position for the transportation vehicle; transportationvehicle detecting means for detecting the transportation vehicle whenthe transportation vehicle is located at the position taught by theteaching means; transfer start detecting means for detecting start ofthe transfer of the material to the transportation vehicle; transfer enddetecting means for detecting end of the transfer of the material to thetransportation vehicle; load computing means for periodically computingweight of the material in the bucket during the transfer; average valuecomputing means for computing an average value of weights of thematerial periodically computed by the load computing means, the weightsof the material including a currently computed weight and apredetermined number of weights computed prior to the currently computedweight; standard deviation computing means for computing, based on theaverage value computed by the average value computing means, a standarddeviation of the weights of the material including the currentlycomputed weight and the predetermined number of weights computed priorto the currently computed weight; true load value determining means forselecting a minimum standard deviation from among the standarddeviations computed by the standard deviation computing means from thestart of the transfer of the material to the transportation vehicleuntil the end of the transfer of same, and judging the average valuebased on which the minimum standard deviation was computed, to be a truevalue of the weight of the material; and weight display means fordisplaying at least an integrated value of the true values determined bythe true load value determining means over a period for which thetransportation vehicle located at the taught position is continuouslydetected by the transportation vehicle detecting means.

This permits the operator of the hydraulic excavator to confirm withease an accurate weight of the material, that is, the amount of load,which has been transferred to each transportation vehicle, thus makingit possible to prevent overloading.

In the work amount detection result display device, the transfer startdetecting means may detect, as the start of the transfer, completion ofscooping of the material with the bucket, and the transfer end detectingmeans may detect, as the end of the transfer, bucket dump operation.

This permits a true value of the weight of the material to be determinedbased on weights detected over a wide range, as in the aforementionedwork amount detection device and method.

In the work amount detection result display device, the weight displaymeans may additionally display the average value of the weights of thematerial computed by the average value computing means.

This makes it easy for the operator of the hydraulic excavator toconfirm also the weight of the material being transferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view exemplifying a manner of how a hydraulic excavatorequipped with a device of the present invention is operated at a worksite such as a mine;

FIG. 2 is a block diagram showing a work amount detection device for ahydraulic excavator according to the present invention;

FIG. 3 is a diagram showing a configuration of a load measuring unitaccording to the present invention;

FIG. 4 is a view illustrating examples of release and transfer rangesaccording to the present invention;

FIG. 5 is a view illustrating other examples of release and transferranges according to the present invention;

FIG. 6 is a time chart illustrating examples of a swing signal, bucketdump operation signal and load W which are input to the load measuringunit of the present invention;

FIG. 7 is a flowchart showing a control routine for a load computingprogram and an operation discrimination program according to the presentinvention;

FIG. 8 is a part of a flowchart showing a control routine for theoperation discrimination program and a release detection programaccording to the present invention;

FIG. 9 is the remaining part of the flowchart continued from the part ofFIG. 8, showing the control routine for the operation discriminationprogram and the release detection program according to the presentinvention;

FIG. 10 is a view illustrating an exemplary arrangement according to thepresent invention wherein distance sensors are installed on the ground;

FIG. 11 is a view illustrating another exemplary arrangement accordingto the present invention wherein the distance sensors are installed onthe ground;

FIG. 12 is a view illustrating an exemplary arrangement according to thepresent invention wherein GPS units are used in place of the distancesensors; and

FIG. 13 is a view illustrating an example of application of the presentinvention to a loading shovel-type hydraulic excavator.

BEST MODE OF CARRYING OUT THE INVENTION

An embodiment of the present invention will be hereinafter describedwith reference to FIGS. 1 through 10.

FIG. 1 exemplifies a manner of operation of a hydraulic excavator 1equipped with a device according to the present invention.

In the figure, reference numeral 11 denotes a boom mounted to arevolving superstructure 2 of the hydraulic excavator 1, 12 denotes boomcylinders for raising and lowering the boom 11, 13 denotes an arm, 14denotes an arm cylinder for swinging the arm 13, 15 denotes a bucket,and 16 denotes a bucket cylinder for swinging the bucket. Referencenumeral 17 denotes a swing device for swinging the revolvingsuperstructure 2 rightward and leftward.

When a dump truck 3 is stopped in front of the hydraulic excavator 1constructed as above, the bucket 15 is operated to scoop mineral ore orearth/sand from an excavation spot, not shown, the revolvingsuperstructure 2 is swung to move the bucket 15 to a release range, thatis, a position above a vessel 4 of the dump truck 3, and the mineral oreor earth/sand is loaded onto the vessel 4. Then, to again load themineral ore or earth/sand, the revolving superstructure 2 of thehydraulic excavator 1 is swung toward the excavation spot. The hydraulicexcavator 1 repeats this sequence of operations several times, to loadthe vessel 4 of the dump truck 3 with a predetermined amount of mineralore or earth/sand. After the loading is completed, the dump truck 3transports the mineral ore or earth/sand to a given location.

FIG. 2 is a block diagram showing a work amount detection device for ahydraulic excavator according to the present invention.

In the figure, reference numeral 121 denotes a bottom chamber of theboom cylinder 12, 122 denotes a rod chamber of the boom cylinder 12, 123denotes a pressure sensor for measuring the pressure of pressure oil inthe bottom chamber 121, 124 denotes a pressure sensor for measuring thepressure of pressure oil in the rod chamber 122, 18 denotes a hydraulicpump for the hydraulic excavator 1, 19 denotes an operating oil tank,and 125 denotes a selector valve inserted between the hydraulic pump 18and the boom cylinder 12.

Reference numeral 141 denotes a bottom chamber of the arm cylinder 14,142 denotes a rod chamber of the arm cylinder 14, 143 denotes a pressuresensor for measuring the pressure of pressure oil in the bottom chamber141, 144 denotes a pressure sensor for measuring the pressure ofpressure oil in the rod chamber 142, and 145 denotes a selector valveinserted between the hydraulic pump 18 and the arm cylinder 14.

Also, reference numeral 161 denotes a bottom chamber of the bucketcylinder 16, 162 denotes a rod chamber of the bucket cylinder 16, 163denotes a pressure sensor for measuring the pressure of pressure oil inthe bottom chamber 161, 164 denotes a pressure sensor for measuring thepressure of pressure oil in the rod chamber 162, and 165 denotes aselector valve inserted between the hydraulic pump 18 and the bucketcylinder 16.

Reference numeral 20 denotes a bucket operation lever and 21 denotes aswing operation lever. As the bucket operation lever 20 is operated, theselector valve 165 is switched to actuate the bucket cylinder 16.

Reference numeral 201 denotes a sensor for detecting an operation of thebucket operation lever 20 in a direction to cause dumping operation ofthe bucket 15, and 202 denotes a sensor for detecting a direction ofoperation (right swing or left swing) of the swing operation lever 21.The sensors 201 and 202 may be sensors for detecting voltage etc. in thecase where the bucket operation lever 20 and the swing operation lever21 are of electric lever type, and may be pressure sensors or pressureswitches in the case where the levers 20 and 21 are of hydraulic pilottype.

Reference numeral 27 denotes a load measuring unit for computing theweight of a load (material) scooped with the bucket 15, such as mineralore or earth/sand, based on various input signals, 22 denotes a boomangle sensor for measuring the angle of rotation of the boom 11 relativeto a supporting pin attached to the base of the boom 11, 23 denotes anarm angle sensor for measuring the angle of rotation of the arm 13relative to a supporting pin attached to the distal end of the boom 11,25 denotes a bucket angle sensor for detecting the angle of rotation ofthe bucket 15, and 24 denotes a swing angle sensor for measuring theswing angle of the swing device 17 which swings the revolvingsuperstructure 2. Also, reference numeral 28 denotes a release positionteaching button for setting a position (release position) where themineral ore or earth/sand is to be released from the bucket 15, and 29denotes a distance sensor (transportation vehicle detecting means)arranged at a front part of the hydraulic excavator 1 for detecting thedistance to the dump truck 3.

Reference numeral 26 denotes a display device (weight display means) fordisplaying the weight of the mineral ore or earth/sand calculated by theload measuring unit 27. Specifically, the display device 26 isconstituted by three display sections, namely, a current load displaysection 26 a, a determined load display section 26 b, and a total loaddisplay section 26 c.

The load measuring unit 27 is input with various signals, which includea bucket dump operation signal S1 from the sensor 201, a right swingsignal S2 and a left swing signal S3 from the sensor 202, a boom bottompressure signal S4 from the pressure sensor 123, a boom rod pressuresignal S5 from the pressure sensor 124, an arm bottom pressure signal S6from the pressure sensor 143, an arm rod pressure signal S7 from thepressure sensor 144, a bucket bottom pressure signal S8 from thepressure sensor 163, a bucket rod pressure signal S9 from the pressuresensor 164, a boom angle signal S10 from the boom angle sensor 22, anarm angle signal S11 from the arm angle sensor 23, a swing angle signalS12 from the swing angle sensor 24, a bucket angle signal S13 from thebucket angle sensor 25, and a distance signal S14 from the distancesensor 29. Based on these signals, the load measuring unit 27 computesthe load in the bucket 15, that is, the weight of mineral ore orearth/sand scooped in the bucket 15, and outputs the resultant data S15indicative of the computed weight to the display device 26.

FIG. 3 shows a configuration of the load measuring unit 27 according tothe present invention, appearing in FIG. 2.

The load measuring unit 27 comprises a computer as its principalcomponent. In the figure, reference numeral 271 denotes an inputinterface provided with A/D converters for receiving the various inputsignals, 272 denotes a central processing unit (CPU) for performingvarious computations and control operations, 273 denotes a timer foroutputting a pulse signal with a fixed period, 274 denotes a randomaccess memory (RAM) for storing results of computations, 275 denotes aread only memory (ROM) storing various processing programs to beexecuted by the CPU 272, and 276 denotes an output interface foroutputting various data to the display device 26.

Specifically, the ROM 275 stores a load computing program 275 a, anoperation discrimination program 275 b, and a release detection program275 c.

Operation of the present invention configured as above will be nowdescribed.

FIGS. 4 and 5 illustrate release ranges used in the operationdiscrimination program 275 b according to the present invention. Therelease range is defined as a swing angle of ±α whose bisector coincideswith a taught position taught by means of the release position teachingbutton 28. Outside the release range is a transfer range. FIG. 4illustrates the case where the dump truck 3 is stopped with its rearfacing the hydraulic excavator 1, and FIG. 5 illustrates the case wherethe dump truck is stopped with its one side facing the excavator.Whichever direction the dump truck 3 is oriented, the dump truck isjudged to be stopped at a proper position near the taught positioninsofar as the distance signal S14 from the distance sensor 29 shows adistance falling within a predetermined range.

FIG. 6 is a time chart exemplifying the arm bottom pressure signal S6,swing signals S2 and S3, bucket dump operation signal S1 and load W, allinput to the load measuring unit 27 of the present invention.

In the illustrated example, the right swing signal S2 turns ON and thusthe hydraulic excavator 1 swings rightward from the excavation positionto the vessel 4 of the dump truck 3, whereupon it is judged by theoperation discrimination program 275 b that the boom 11 has entered therelease range from the transfer range. Subsequently, the bucket dumpoperation signal S1 turns ON, so that the hydraulic excavator 1 loadsthe dump truck 3 with mineral ore or earth/sand. After the loading iscompleted, the left swing signal S3 turns ON and thus the hydraulicexcavator 1 swings leftward to the excavation position, whereupon it isjudged that the boom 11 has left the release range and entered thetransfer range. Alternatively, the hydraulic excavator 1 may be operatedto swing rightward after the loading.

The load W indicates the weight of mineral ore or earth/sand scooped inthe bucket 15. The load W is computed at regular intervals by the loadcomputing program 275 a, following a calculation method (load computingmeans, load computing step) explained below, for example.

A force exerted to support the boom 11, the arm 13 and the bucket 15containing mineral ore or earth/sand can be obtained from the boombottom pressure signal S4 and the boom rod pressure signal S5 input tothe load measuring unit 27, or from the arm bottom pressure signal S6and the arm rod pressure signal S7 input to the unit 27. Also, thecenters of gravity of the boom 11, arm 13 and bucket 15 can becalculated from the boom angle signal S10, the arm angle signal S11 andthe bucket angle signal S13. Thus, the moment around the supporting pinattached to the base of the boom 11 can be obtained from the calculatedcenters of gravity and the known weights of the boom 11, arm 13 andempty bucket 15. Then, the weight of the mineral ore or earth/sandcontained in the bucket 15 is calculated in consideration of theequilibrium between the aforementioned supporting force and the momentaround the supporting pin attached to the base of the boom 11. Duringswinging motion, the calculated weight is corrected using a centrifugalforce corresponding to the swing speed. This calculation method is knownin the art, as disclosed in Examined Japanese Patent Publication No.H04-44930.

In the example shown in FIG. 6, during the rightward swinging motion,the load W shows a large value because the boom 11 is then swingingtoward the vessel 4 of the dump truck 3 after scooping mineral ore orearth/sand at the excavation position. During the leftward swingingmotion, on the other hand, the load W shows a small value because theboom 11 is then returning to the excavation position after loading themineral ore or earth/sand onto the dump truck 3.

FIGS. 7 to 9 are flowcharts illustrating control routines for the loadcomputing program 275 a, the operation discrimination program 275 b andthe release detection program 275 c according to the present invention.In the following, the invention will be described with reference to theflowcharts.

In Step M1 in FIG. 7, it is determined based on the arm bottom pressuresignal S6, shown in FIG. 6, whether or not the arm bottom pressure hasdecreased from a level higher than a predetermined pressure P₁ down to alevel lower than the pressure P₁. If the decision is affirmative (Yes),it is judged that excavation has ended; therefore, an excavation endflag is set ON in Step M2, and the routine proceeds to Step M3. If thedecision is negative (No), it is judged that excavation or some otheroperation is in process, and the routine directly proceeds to Step M3.

In Step M3, it is determined whether or not the arm bottom pressure hasincreased from a level lower than a predetermined pressure P₂ up to alevel higher than the pressure P₂. If the decision is affirmative (Yes),it is judged that excavation has been started; therefore, the excavationend flag is set OFF in Step M4, and the routine proceeds to Step M5. Ifthe decision is negative (No), it is judged that excavation or someother operation is in progress, and the routine directly proceeds toStep M5.

In Step M5, it is determined whether or not the excavation end flag isON (transfer start detecting means, transfer start detecting step). Ifthe decision is affirmative (Yes) and thus the flag is ON, that is, ifthe arm bottom pressure has decreased from above the predeterminedpressure P₁ to a level lower than the pressure P₁, it can be concludedthat excavation has ended. In this case, an average value W_(ave) of nloads W (n=predetermined number) detected in the past is calculated(average value computing means, average value computing step), in StepM6. Then, in Step M7, a standard deviation σ is calculated from theaverage load W_(ave) and a currently detected load W (standard deviationcomputing means, standard deviation computing step), according to thefollowing equation (1):σ=(1/(n−1)Σ(W _(i) −W _(ave))²)^(1/2)  (1)where W_(i) represents each of n loads W calculated in the past (i=1, .. . , n).

Thus, the standard deviation is repeatedly calculated while updating theload W each time the load W is calculated. The calculation of thestandard deviation σ is repeated until a bucket dump operation isperformed following the transfer of mineral ore or earth/sand, that is,over the longest possible transfer period until the bucket dumpoperation signal S1 is detected and thus the scooped mineral ore orearth/sand is released (see FIG. 6).

In Step M8, the previously calculated standard deviation σ_(now), issubstituted for a previous standard deviation σ_(prev), and in Step M9,the standard deviation σ calculated in Step M7 is set as the new currentstandard deviation σ_(now).

Then, in Step M10, the previous standard deviation σ_(prev) and thecurrent standard deviation σ_(now) are compared with each other, todetermine a minimum standard deviation σ_(min) (true load valuedetermining means, true load value determining step). If the decision isaffirmative (Yes), that is, if the standard deviation σ_(now) is smallerand thus judged to be the minimum standard deviation σ_(min), theaverage load W_(ave) used to calculate the standard deviation σ_(now) isstored as a true load W_(true), in Step M11. If the decision is negative(No) and the previous standard deviation σ_(prev) is smaller, theroutine is ended.

If the decision in Step M5 is negative (No) and the flag is OFF, it canbe concluded that excavation is not finished yet. In this case, thestandard deviation σ_(now) is set to a maximum value, followed bytermination of the routine.

While the distance signal S14 from the distance sensor 29 shows adistance falling within the predetermined range, it is judged that thedump truck 3 is located in a proper position and thus that the vessel 4can be loaded with material. In this case, in Step M21 in FIG. 8, it isdetermined based on the bucket dump operation signal S1 whether or notbucket dump operation has been started to release the material. In thecase where the bucket operation lever 20 is a hydraulic pilot type, thebucket dump operation signal S1 is detected by determining whether ornot the level of the pressure signal has exceeded a fixed value, andwhere the bucket operation lever 20 is an electric lever, the bucketdump operation signal is detected by determining whether or not thelevel of the voltage signal has exceeded a fixed value (transfer enddetecting means, transfer end detecting step).

If the decision in Step M21 is affirmative (Yes) and thus bucket dumpoperation has been started, the current true load W_(true) stored inStep M11 is acquired as an average load associated with the minimumstandard deviation σ_(min) at the start of bucket dump operation, inStep M22. Subsequently, in Step M23, an end time of the bucket dumpoperation is acquired. Then, in Step M24, a bucket dump operationdiscrimination flag F_(b) is set ON, and the routine proceeds to StepM25. On the other hand, if the decision in Step M21 is negative (No) andit is judged that no bucket dump operation is being performed, theroutine directly proceeds to Step M25.

In practice, the acquisition of the true load W_(true) at the start ofthe bucket dump operation and the acquisition of the end time of thebucket dump operation are performed within bucket dump operationdiscriminating means, not shown. Accordingly, the true load W_(true) andthe bucket dump operation end time acquired in this manner are used inSteps M22 and M23, respectively.

In Step M25, it is determined whether or not a transition of the swingangle from the transfer range to the release range has occurred. If theswing angle has entered the release range, the load W then measured isstored as a load W_(in), in Step M26. Subsequently, in Step M27, thetime of the transition is stored, and in Step M28, a releasedetermination flag F_(d1) is set ON. If the decision in Step M25 isnegative (No) and thus it is judged that the transition of the swingangle from the transfer range to the release range has not occurred, theroutine directly proceeds to Step M29.

In Step M29, it is determined whether or not a transition of the swingangle from the release range to the transfer range has occurred. If theswing angle has entered the transfer range, the load W then measured isstored as a load W_(out), in Step M30. Subsequently, in Step M31, arelease determination flag F_(d2) is set ON, and the routine proceeds tothe next step. On the other hand, if the decision in Step M29 isnegative (No) and it is judged that the transition of the swing anglefrom the release range to the transfer range has not occurred, theroutine directly proceeds to Step M32.

In Step M32 in FIG. 9, it is determined whether all of the bucket dumpoperation discrimination flag F_(b) and release determination flagsF_(d1) and F_(d2) are ON or not. If the decision is affirmative (Yes)and thus all of the flags are ON, the routine proceeds to Step M33. Ifthe decision is negative (No), the routine is ended.

In Step M33, the order in which the flags were set ON is determined. Ifthe bucket dump operation discrimination flag F_(b) and the releasedetermination flag F_(d2) were set ON in this order, it can be concludedthat the swing angle has entered the transfer range after bucket dumpoperation was performed in the release range. In this case, the routineproceeds to Step M34.

In Step M34, whether mineral ore or earth/sand as the scooped materialhas actually been released or not is determined by comparing thedifference between the loads W_(in) and W_(out), stored beforehand, witha load criterion. The load criterion may be “0” or be set to a certainvalue at and above which the load W is to be judged effective. If thedecision is affirmative (Yes) and it is judged that the scooped materialhas been released, the routine proceeds to Step M35.

In Step M35, the bucket dump operation end time stored in Step M23 iscompared with the time stored in Step M27, that is, the time of thetransition of the swing angle from the transfer range to the releaserange, and the true load W_(true) which was stored at the time of thebucket dump operation immediately after the transition is output to theoutput interface 276 as the weight of the material released onto thevessel 4 of the dump truck 3.

The signal output to the output interface 276 is supplied to the displaydevice 26, and an integrated value of the true loads W_(true) isdisplayed at the determined load display section 26 b which is adaptedto display an integrated value of the true loads obtained over a periodfrom the time the release position is taught until the next releaseposition is taught. In the case where the position of the dump truck 3is automatically determined by the distance sensor 29, the releaseposition teaching button 28 need not be pressed, and besides, theintegrated value of the true loads W_(true) is displayed at thedetermined load display section 26 b over a period from the time thearrival of the dump truck 3 is detected until the dump truck 3 leavesthe loading position. This permits the operator to be notified of theamount of the material loaded onto the dump truck 3, making it possibleto prevent overloading.

A signal indicative of the aforementioned average load W_(ave) is alsosuccessively output to the display device 26, and the average loadW_(ave) is displayed at the current load display section 26 a.

Also, the total load display section 26 c displays an integrated valueof the true loads W_(true) calculated over a predetermined work shiftperiod from the time an engine ignition key, not shown, of the hydraulicexcavator 1 is turned ON until the engine ignition key is turned OFF.Data on the integrated value of the true loads W_(true) can betransferred to outside through the output interface 276, for example,and also can be cleared by pressing a reset button, not shown, for everywork shift.

After the true load W_(true) is output, the bucket dump operationdiscrimination flag F_(b) is set OFF in Step M36, and the releasedetermination flags F_(d1) and F_(d2) are set OFF in Step M37, followedby termination of the routine. If the condition in Step M35 fails to befulfilled, it is judged that no release of material onto the dump truck3 took place, and the routine is ended after executing Steps M36 andM37.

Thus, according to the present invention, the excavation and releaseoperation of the hydraulic excavator 1 are automatically detected, andan average load W_(ave) obtained during a period in which the standarddeviation σ of detected loads shows a minimum standard deviation σ_(min)and thus the load W is most stable over a wide range from the end ofexcavation to the start of release operation is judged to be a truevalue of the load such as mineral ore or earth/sand, that is, the trueload W_(true). Accordingly, the load W such as mineral ore or earth/sandreleased from the hydraulic excavator 1 onto the vessel 4 of the dumptruck 3 can be accurately measured, without being influenced by theoperation (boom moving speed, arm moving speed, bucket height, etc.) ofthe hydraulic excavator 1 during the transfer of the scooped material tothe dump truck 3. This not only permits an accurate load W to bedisplayed at the display device 26, making it easy for the operator toascertain the accurate load W, but also permits the true load W_(true)to be integrated for each work shift, thus enabling a supervisor etc. tomanage the output of mineral ore or earth/sand with accuracy.

Further, it is confirmed by means of the distance sensor 29 that thedump truck 3 is located at a proper position close to the taughtposition, before mineral ore or earth/sand is loaded onto the vessel 4.It is therefore possible to calculate the amount of load on the dumptruck 3 with accuracy and also to easily manage an actual output ofmineral ore or earth/sand, without the need for the operator to pressthe release position teaching button 28.

While the preferred embodiment has been described, the present inventionis not limited to the foregoing embodiment.

For example, in the foregoing embodiment, the distance sensor 29 isarranged at the front part of the hydraulic excavator 1. Alternatively,as shown in FIGS. 10 and 11, distance sensors 291 may be arranged on theground at locations suited for the position and orientation of thestopped dump truck 3, and detection signals transmitted from radiotransmitters 292 may be received by a receiver 293 attached to thehydraulic excavator 1.

Further, as shown in FIG. 12, the hydraulic excavator 1 and the dumptruck 3 may both be equipped with GPS units 295 and 294, respectively,so that a position detection signal transmitted from a radio transmitter296 mounted on the dump truck 3 may be received by a receiver 297mounted on the hydraulic excavator 1, to detect a relative positionbetween the excavator 1 and the dump truck 3. With this arrangement, therelative position between the hydraulic excavator 1 and the dump truck 3can be obtained, as distinct from the case of using the distance sensor.It is therefore possible to ascertain whether the dump truck 3 isstopped at a proper position or not based on, for example, the distancebetween the GPS units 294 and 295 obtained from distances L_(x0) andL_(y0) shown in FIG. 12, and a relative angle θ_(t). It is also possibleto accurately locate the vessel 4 based on information about the vesselcorner positions {(X_(t1), Y_(t1), Z_(t1)), (X_(t2), Y_(t2), Z_(t2)),(X_(t3), Y_(t3), Z_(t3)) (X_(t4), Y_(t4), Z_(t4))}. In the case of usingthe GPS units 294 and 295, therefore, the taught position can beautomatically set, and it is possible to calculate the amount of load onthe dump truck 3 with accuracy and also to easily manage an actualoutput of mineral ore or earth/sand, without the need for the operatorto press the release position teaching button 28.

Also, in the foregoing embodiment, bucket dump operation is detectedbased on the bucket dump operation signal S1 from the sensor 201connected to the bucket operation lever 20. Alternatively, an anglesensor for detecting the bucket swing angle or a displacement sensor fordetecting the displacement of the bucket cylinder 16 may be used so thatbucket dump operation may be detected based on information from theangle sensor or the displacement sensor.

In the above embodiment, the standard deviation σ is obtained, but σ²may be derived instead because the aim of calculating σ is to obtaindispersion of the load W.

Further, in the foregoing embodiment, the end of excavation is detectedbased on the arm bottom pressure signal S6, but may alternatively bedetected based on the bucket bottom pressure signal S8. Moreover, in thecase where the arm cylinder 14 is inversely mounted to the hydraulicexcavator 1, the arm rod pressure signal S7 is used to detect the end ofexcavation, and where the bucket cylinder 16 is inversely mounted, thebucket rod pressure signal S9 is used to detect the end of excavation.

In the above embodiment is described the backhoe type hydraulicexcavator 1 by way of example. It is to be noted that the presentinvention is also suitably applicable to a loading shovel type hydraulicexcavator 1′ shown in FIG. 13. In the figure, reference numeral 12′denotes a boom cylinder for raising and lowering a boom 11′ of theloading shovel type hydraulic excavator 1′, 14′ denotes an arm cylinderfor swinging an arm 13′, and 16′ denotes a bucket cylinder for swinginga bucket 15′. Thus, the true load W_(true) can be obtained, like theforegoing embodiment, by detecting the boom bottom pressure and boom rodpressure of the boom cylinder 12′, the arm bottom pressure and arm rodpressure of the arm cylinder 14′, the boom angle, the arm angle and thebucket angle. Also in this case, the load W of mineral ore or earth/sandreleased from the hydraulic excavator 1 onto the vessel 4 of the dumptruck 3 can be measured with accuracy.

Furthermore, in the above embodiment, the position (release range) forreleasing mineral ore or earth/sand from the bucket 15 and the transferrange are set in two dimensions by the release position teaching button28. The present invention is, however, not limited to such range settingand may be configured so as to set the release and transfer ranges inthree dimensions (in the height direction as well). In this case, thepresent invention can cope with a situation where the vessels 4 of dumptrucks 3 are at different heights from the ground, for example.

1. A work amount detection device for a hydraulic excavator which scoopsa material with a bucket thereof and transfers the material to adifferent location, said work amount detection device comprising:transfer start detecting means for detecting start of the transfer ofthe material to the different location; transfer end detecting means fordetecting end of the transfer of the material to the different location;load computing means for periodically computing weight of the materialin the bucket during the transfer; average value computing means forcomputing an average value of weights of the material periodicallycomputed by said load computing means, the weights of the materialincluding a currently computed weight and a predetermined number ofweights computed prior to the currently computed weight; standarddeviation computing means for computing, based on the average valuecomputed by said average value computing means, a standard deviation ofthe weights of the material including the currently computed weight andthe predetermined number of weights computed prior to the currentlycomputed weight; and true load value determining means for selecting aminimum standard deviation from among the standard deviations computedby said standard deviation computing means from the start of thetransfer of the material to the different location until the end of thetransfer of same, and judging the average value based on which theminimum standard deviation was computed, to be a true value of theweight of the material.
 2. A work amount detection device for ahydraulic excavator which scoops a material with a bucket thereof andtransfers the material to a transportation vehicle, said work amountdetection device comprising: teaching means for teaching a position forthe transportation vehicle; transportation vehicle detecting means fordetecting the transportation vehicle when the transportation vehicle islocated at the position taught by said teaching means; transfer startdetecting means for detecting start of the transfer of the material tothe transportation vehicle; transfer end detecting means for detectingend of the transfer of the material to the transportation vehicle; loadcomputing means for periodically computing weight of the material in thebucket during the transfer; average value computing means for computingan average value of weights of the material periodically computed bysaid load computing means, the weights of the material including acurrently computed weight and a predetermined number of weights computedprior to the currently computed weight; standard deviation computingmeans for computing, based on the average value computed by said averagevalue computing means, a standard deviation of the weights of thematerial including the currently computed weight and the predeterminednumber of weights computed prior to the currently computed weight; andtrue load value determining means for selecting a minimum standarddeviation from among the standard deviations computed by said standarddeviation computing means from the start of the transfer of the materialto the transportation vehicle until the end of the transfer of same, andjudging the average value based on which the minimum standard deviationwas computed, to be a true value of the weight of the material.
 3. Thework amount detection device according to claim 1, wherein said transferstart detecting means detects, as the start of the transfer, completionof scooping of the material with the bucket, and said transfer enddetecting means detects, as the end of the transfer, bucket dumpoperation.
 4. A work amount detection method for a hydraulic excavatorwhich scoops a material with a bucket thereof and transfers the materialto a different location, said work amount detection method comprising: atransfer start detecting step of detecting start of the transfer of thematerial to the different location; a transfer end detecting step ofdetecting end of the transfer of the material to the different location;a load computing step of periodically computing weight of the materialin the bucket during the transfer; an average value computing step ofcomputing an average value of weights of the material periodicallycomputed in said load computing step, the weights of the materialincluding a currently computed weight and a predetermined number ofweights computed prior to the currently computed weight; a standarddeviation computing step of computing, based on the average valuecomputed in said average value computing step, a standard deviation ofthe weights of the material including the currently computed weight andthe predetermined number of weights computed prior to the currentlycomputed weight; and a true load value determining step of selecting aminimum standard deviation from among the standard deviations computedin said standard deviation computing step from the start of the transferof the material to the different location until the end of the transferof same, and judging the average value based on which the minimumstandard deviation was computed, to be a true value of the weight of thematerial.
 5. The work amount detection method according to claim 4,wherein in said transfer start detecting step, completion of scooping ofthe material with the bucket is detected as the start of the transfer,and in said transfer end detecting step, bucket dump operation isdetected as the end of the transfer.
 6. A work amount detection resultdisplay device for a hydraulic excavator which scoops a material with abucket thereof and transfers the material to a different location, saidwork amount detection result display device comprising: transfer startdetecting means for detecting start of the transfer of the material tothe different location; transfer end detecting means for detecting endof the transfer of the material to the different location; loadcomputing means for periodically computing weight of the material in thebucket during the transfer; average value computing means for computingan average value of weights of the material periodically computed bysaid load computing means, the weights of the material including acurrently computed weight and a predetermined number of weights computedprior to the currently computed weight; standard deviation computingmeans for computing, based on the average value computed by said averagevalue computing means, a standard deviation of the weights of thematerial including the currently computed weight and the predeterminednumber of weights computed prior to the currently computed weight; trueload value determining means for selecting a minimum standard deviationfrom among the standard deviations computed by said standard deviationcomputing means from the start of the transfer of the material to thedifferent location until the end of the transfer of same, and judgingthe average value based on which the minimum standard deviation wascomputed, to be a true value of the weight of the material; and weightdisplay means for displaying at least an integrated value of the truevalues determined by said true load value determining means over apredetermined period.
 7. The work amount detection result display deviceaccording to claim 6, wherein said weight display means displays anintegrated value of the true values determined by said true load valuedetermining means over a period from the time an engine ignition key ofthe hydraulic excavator is turned ON until the engine ignition key isturned OFF.
 8. A work amount detection result display device for ahydraulic excavator which scoops a material with a bucket thereof andtransfers the material to a transportation vehicle, said work amountdetection result display device comprising: teaching means for teachinga position for the transportation vehicle; transportation vehicledetecting means for detecting the transportation vehicle when thetransportation vehicle is located at the position taught by saidteaching means; transfer start detecting means for detecting start ofthe transfer of the material to the transportation vehicle; transfer enddetecting means for detecting end of the transfer of the material to thetransportation vehicle; load computing means for periodically computingweight of the material in the bucket during the transfer; average valuecomputing means for computing an average value of weights of thematerial periodically computed by said load computing means, the weightsof the material including a currently computed weight and apredetermined number of weights computed prior to the currently computedweight; standard deviation computing means for computing, based on theaverage value computed by said average value computing means, a standarddeviation of the weights of the material including the currentlycomputed weight and the predetermined number of weights computed priorto the currently computed weight; true load value determining means forselecting a minimum standard deviation from among the standarddeviations computed by said standard deviation computing means from thestart of the transfer of the material to the transportation vehicleuntil the end of the transfer of same, and judging the average valuebased on which the minimum standard deviation was computed, to be a truevalue of the weight of the material; and weight display means fordisplaying at least an integrated value of the true values determined bysaid true load value determining means over a period for which thetransportation vehicle located at the taught position is continuouslydetected by said transportation vehicle detecting means.
 9. The workamount detection result display device according to claim 6, whereinsaid transfer start detecting means detects, as the start of thetransfer, completion of scooping of the material with the bucket, andsaid transfer end detecting means detects, as the end of the transfer,bucket dump operation.
 10. The work amount detection result displaydevice according to claim 6, wherein said weight display meansadditionally displays the average value of the weights of the materialcomputed by said average value computing means.